1. Field of the Invention
The present invention relates to an optical scanning apparatus included in an electrophotographic image forming apparatus, such as a laser printer or a digital copier.
2. Description of the Related Art
An example of an optical scanning apparatus included in an electrophotographic image forming apparatus is structured such that a plurality of light source units are supported in an optical box. Japanese Patent Laid-Open No. 2008-268239 discloses a method for positioning and securing light source units when the light source units are arranged in a rotation axis direction of a rotating polygon mirror. FIG. 14 is a perspective view of a part of an optical scanning apparatus disclosed in Japanese Patent Laid-Open No. 2008-268239. As illustrated in FIG. 14, a tunnel-shaped hollow region is formed in a side surface of an optical box 79, and a plurality of light source units 71K and 71M are arranged close to each other in the Z direction (rotation axis direction) in the hollow region. Positioning in the Z direction is achieved as follows. That is, the light source unit 71K is positioned by causing a cylindrical portion of a light source holder 72K to abut on an abutting portion 76K formed on a positioning unit 79a of the optical box 79. Similarly, the light source unit 71M is positioned by causing a cylindrical portion of a light source holder 72M to abut on an abutting portion 76M formed on a positioning unit 79b of the optical box 79.
Positioning in the main scanning direction (Y direction) is achieved by causing the cylindrical portions of the light source holders 72K and 72M of the light source units 71K and 71M to abut on the abutting portions 75K and 75M, respectively, of the optical box 79. The light source holders 72K and 72M are fixed to the optical box 79 by pressing the light source holders 72K and 72M against the abutting portions 75K, 75M, 76K, and 76M with springs 77 in directions shown by arrows U1 and U2.
In order for the abutting portions 76K and 76M to achieve sufficient positioning accuracy, the two positioning units 79a and 79b having the abutting portions 76K and 76M of the optical box 79 need to have certain thickness and strength so as not to easily deform when the light source units 71K and 71M abut thereon.
The positioning units 79a and 79b are disposed outside the light source units 71K and 71M, respectively, in the rotation axis direction of a rotating polygon mirror. Therefore, when the positioning units 79a and 79b of the optical box 79 are formed so as to have certain strength, the size of the optical box 79 in the rotation axis direction of the rotating polygon mirror is increased. As a result, the size of the optical scanning apparatus and the size of an image forming apparatus including the optical scanning apparatus are increased.